When we listen to ordinary music from speakers, speakers, TV and similar external sources, the sound first enters the ear, which by nature is an excellent resonator. Due to this, the sound waves are amplified and regulated in a natural way. The harm of headphones is not due to the fact that a certain device is placed in the ears.
After all, the same earplugs or noise-protective headphones are not considered dangerous. The very transmission of sound, especially loud sound, backfires. However, when using headphones, the sound is not naturally amplified, and the owner of the player adjusts the volume level at his own discretion. However, due to the fact that initially we usually want to turn on the music louder, we involuntarily exceed the permissible noise standards, and as a result, very quickly - literally in a few days - we can significantly reduce the sharpness of our own hearing.
An additional harm from in-ear headphones is that uncontrolled pressure is created on the auricle. Before this pressure, coupled with prolonged intense noise exposure, the human ear is completely defenseless, because the natural hearing aid "turns on the option" of self-defense against a short rumble, but not from constant loud noise.